Power generating processes that are based on combustion of carbon containing fuel typically produce carbon dioxide (CO2) as a byproduct. It may be desirable to capture or otherwise separate the CO2 from the gas mixture to prevent the release of CO2 into the environment, and/or to utilize CO2 in the power generation process or in other processes.
However, typical CO2 capture processes, such as, for example, an aqueous amine-based process (MEA-based process), may have limitations, for example, the process can sometimes result in sharp increases in the viscosity of the liquid absorbent, which can decrease the mass transfer of CO2 into the sorbent. To avoid this problem, the concentration of amines in the absorbent stream may be maintained at low levels (using carrier solvents), which may greatly reduce absorbing capacity, as compared to the theoretical capacity of the neat absorbent. Moreover, energy consumption in the amine process may be high, due in large part to the need for heating and evaporation of the carrier solvent (for example, water).
There are many properties that desirably would be exhibited, or enhanced, in any CO2 capture technology and absorbents contemplated to be a feasible alternative to the currently utilized MEA-based processes. For example, any such absorbent would desirably exhibit a high net CO2 capacity, and could provide lower capital and operating costs (less material volume required to heat and cool, therefore less energy required). A lower heat of reaction would mean that less energy would be required to release the CO2 from the material. Absorbents with lower viscosities would provide improved mass transfer, reducing the size of equipment needed, as well as a reduction in the cost of energy to run it.
Thus, there is a need for CO2-capture absorbents and methods of use thereof that optimize as many of the above desired properties as possible. Further, there is a need for CO2-capture absorbents and methods of use thereof such that the absorbents have low viscosity and low heat of reaction.